Popular chord progressions in the key of C

Progression

Chords

I-IV-V

C-F-G

I-IV-I-V

C-F-C-G

I-V-vi-IV

C-G-Am-F

I-ii-IV-V

C-Dm-F-G

I-vi-ii-V

C-Am-Dm G

I-vi-IV-V

C-Am-F-G

Why are these the chords in the key of C major? (the theory)

The chords in C will root on the notes along the C major scale, since all chords in a major key are formed by notes from their respective diatonic scale. Oh, if you're a beginner guitar player and lost track already, you'll want to get familiar with the major scale on guitar before continuing this lesson.

The C major scale has 7 notes, each with a corresponding scale degree:

Degree: 1 2 3 4 5 6 7 1(octave)
Note: C D E F G A B C

But how do we know which chord will be major or minor? Starting from a given root note, we need to form its triad in a way which leaves the chord constructed only from notes that can be found on the C major scale.

This means that starting from each root note, we’ll count out the 1st 3rd and 5th degrees along the major scale of that given root note. If any note is not on the C major scale, we’ll have to flatten it to make it a note that can be found on the C major scale. Confusing? Have no fear, we'll get to some examples shortly.

We’ll be differentiating 3 triads:

Major triad (major chords) with scale degrees 1 3 5

Minor triad (minor chords) with scale degrees 1 b3 5

Diminished triads (diminished chords) with scale degrees 1 b3 b5

Now let’s calculate the quality of each chord in the key of C.

C major

Note: C D E F G A B C
Triad: 1 3 5
This gives us the notes C, E and G, which is the C major triad, therefore the first chord in the key of C is C major.

D minor

Note: D E F# G A B C# D
Triad: 1 3 5
So our 3rd note for would be an F#, but we can’t have that, since that note is not in the key of C major (not on the C major scale). We have to lower the 3rd to the flattened 3rd.Note: D E F G A B C# D
Triad: 1 b3 5
This gives us the notes D, F and A, which is the D minor triad. All of these notes are on the C major scale as well, therefore the second chord in the key of C is D minor.

E minor

Note: E F# G# A B C# D# E
Triad: 1 3 5
So our 3rd note would be a G#, but we can’t have that, since that note is not in the key of C. We have to lower the 3rd to the flattened 3rd.Note: E F# G A B C# D# E
Triad: 1 b3 5
This gives us the notes E, G and B, which is the E minor triad, therefore the third chord in the key of C is E minor.

F major

Note: F G A Bb C D E F
Triad: 1 3 5
This time we’re in luck, the 1st, 3rd and 5th of the F major scale are in the key of C, so we don’t need to modify any of the notes. We get the notes F, A and C, which is the F major triad, therefore the fourth chord in the key of C is F major.

G major

Note: G A B C D E F# G
Triad: 1 3 5
Again, the 1st, 3rd and 5th of the G major scale are in the key of C, so we don’t need to modify any of the notes. We get the notes G, B and D, which is the G major triad, therefore the fifth chord in the key of C is G major.

A minor

Note: A B C# D E F# G# A
Triad: 1 3 5
Again, we need to modify our 3rd note, which would be a C#, since that note is not in the key of C. We have to lower the 3rd to the flattened 3rd.Note: A B C D E F# G# A
Triad: 1 b3 5
This gives us the notes A, C and E, which is the A minor triad, therefore the sixth chord in the key of C is A minor.

B diminished

Note: B C# D# E F# G# A# B
Triad: 1 3 5
Ohoh, now we need to flatten the 3rd AND the 5th, since neither the D# or the F# are on the C major scale.Note: B C# D E F G# A# B
Triad: 1 b3 b5
This gives us the notes B, D and F, which is the B diminished triad, therefore the seventh chord in the key of C is B diminished.

And that's about it, you should now know the intricacies of chords in the key of C. The above is of course true not just for guitar chords, but chords in general.

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